Engine management system

ENGINE MANAGEMENT SYSTEM

The Modular Engine Management System (MEMS) controls the fuel injection and programmed ignition systems. The Engine Control Module (ECM) monitors the conditions required for optimum combustion of fuel in the cylinders through sensors located at strategic points around the engine. From these sensor inputs, the engine control module can adjust the timing and quantity of fuel being delivered to the cylinders.

The main features are as follows:

• A single ECM controls the fuel injection system and the programmed ignition system. The ECM incorporates short circuit protection and can store intermittent faults on certain inputs. TestBook can interrogate the ECM for these stored faults.
• The ECM is electronically immobilised preventing the engine from being started unless it receives a coded signal from the anti-theft control unit.
• The ECM uses the speed/density method of air flow measurement to calculate fuel delivery. This method measures the inlet air temperature and inlet manifold pressure and assumes that the engine is a calibrated vacuum pump with its characteristics stored in the ECM. In conjunction with the throttle position sensor the ECM can then determine the correct amount of fuel to be injected.
• If certain system inputs fail, the ECM implements a back-up facility to enable the system to continue functioning, although at a reduced level of performance.
• A separate diagnostic connector, located on a bracket forward of the centre console on the RH side, allows engine tuning or fault diagnosis to be carried out using TestBook without disconnecting the ECM harness multiplug.
• The ECM harness multiplug incorporates specially plated pins to minimise oxidation and give improved reliability.
• The ECM also controls the operation of the radiator and air conditioning cooling fans, based on signals received from the engine coolant temperature sensor. If an abnormally high engine temperature is detected the ECM will inhibit the operation of the air conditioning compressor.

IGNITION SYSTEM

The ECM determines the optimum ignition timing based on the signals it receives from the following sensors:

1. Crankshaft position sensor - Engine speed and crankshaft position.
2. Manifold absolute pressure sensor - Engine load
3. Coolant temperature sensor - Engine temperature
4. Knock sensor - Engine noise and vibration (’T’ series engine)

MEMS does not use centrifugal or vacuum advance, timing being controlled by the ECM which is energised by the main relay, within the relay module.

Spark distribution is achieved by the ECM switching on each coil once during each revolution of the crankshaft.

CAUTION: DO NOT run or crank the engine with a spark plug lead disconnected unless the spark can jump to the block. If both leads from a coil are disconnected, disconnect the LT connector. The voltage in the LT side of the coil can be in excess of 400V.